Presser foot adjusting means



Oct. 21, 1969 D. R. CASH PRESSER FOOT ADJUSTING MEAN 2 Sheets-Sheet 1 Filed 001:. 2, 1967 PITMAN ll INVENTOR.

DAVID R. CASH ATTORNEY Oct. 21, 1969 D. R. CASH 3,473,497

PRESSER FOOT ADJUSTING MEANS Filed Oct. 2, 1967 .2 Sheets-Sheet 2 INVENTOR.

DAVID R. CASH BY Mm ATTORNEY 3,473,497 PRESSER FOOT ADJUSTING MEANS David R. Cash, Louisville, Ky., assignor to James Cash Machine Co., Louisville, Ky., a corporation of Kentucky Filed Oct. 2, 1967, Ser. No. 672,096 Int. Cl. Db 29/02 US. Cl. 112239 2 Claims ABSTRACT OF THE DISCLOSURE A pitman (which interconnects a sewing machine driveshaft eccentric with a rock shaft lever so as to convert rotary motion of the drive shaft into reciprocating motion to swing the rock shaft lever back and forth) has its connection to the rock shaft lever made adjustable to vary the radius of the rock shaft lever from a short radius providing a large presser foot stroke having a high bottom elevation to accommodate a large sewing thickness to a larger radius providing a shorter presser foot stroke having a lower bottom elevation to accommodate a smaller sewing thickness.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to improvements in sewing machines of the type having (1) a rotary drive shaft, which reciprocates a sewing needle, (2) an oscillating rock shaft, which reciprocates a presser foot and (3) a pitman, which connects a drive shaft eccentric to a rock shaft lever to convert rotary motion of the drive shaft into reciprocating motion which swings the rock shaft lever back and forth. More particularly, the present invention relates to improvements in the means for adjusting thi motion changing connection for presser foot adjustment purposes to accommodate a range of different sewing thicknesses.

Description of the prior art To render a sewing machine capable of operating over a wide range of sewing thicknesses, it is necessary to vary the elevation of the presser foot at the bottom of its stroke because its lowermost elevation, when sewing thick materials, is higher than its lowermost elevation, when sewing thin materials. It is also necessary to vary the amplitude of the presser foot stroke because thick materials require a longer stroke than do thin materials. To accomplish stroke adjustments of this character, the Zeier Patents 2,428,762 and 2,445,297 typically propose to adjust the rock shaft actuating eccentric.

SUMMARY OF THE INVENTION Objects of the invention The principal objects of the present invention are: to provide a simply constructed easily operated means of effecting both adjustments in one easily and quickly performed operation which does not require any adjustment or replacement of the rock shaft actuating eccentric; and to provide a presser foot adjusting mechanism which can be readily applied to existing sewing machines.

Statement of the invention All of the objects of the present invention may be readily achieved simply by providing means for changing the location of the connection of the pitman to the Work shaft operating lever to vary the radius of that lever from a short radius, which provides a larger presser foot stroke having a high bottom elevation to accommodate a large sewing thickness, to a larger radius, which provides a shorter presser foot stroke having a lower bottom elevation to accommodate a smaller sewing thickness.

. nited States Patent 0 3,473,497 Patented Oct. 21, 1969 BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated in the drawings wherein:

FIG. 1 is a top plan view of a sewing machine in which the present invention is incorporated;

FIG. 2 is an end elevational view showing the sewing end of the machine at the right end of FIG. 1;

FIG. 3 is a left end elevational View of the machine shown in FIGS. 1 and 2;

FIG. 4 is a graph illustrating the change, in radius and angle of oscillation of the rock shaft lever, which results in the practice of the present invention; and

FIG. 5 is a diagrammatic view illustrating the lengths (and bottom elevation) of the presser foot strokes obtained in FIG. 4 when the radii of the rock-shaft operating-lever are short and long respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT The sewing head shown in FIGS. 1-3 conventionally includes: a head frame 1; a main drive shaft 2; a needle 3 carried by a vertically reciprocating needle bar 4 which is connected to the main drive shaft 2 for vertical reciprocation upon the rotary movement of that shaft; a presser foot 5 carried by a vertically reciprocating presser foot bar 6; and means for reciprocating the presser foot 5 in time-phase relationship to the needle 3, said means including a spring 7 on the presser foot bar 6, an arm 8 for reciprocating the presser foot bar 6, a rock shaft 9 for oscillating arm 8; a rock shaft lever 10 for rocking shaft 9, a pitman 11 connecting with an eccentric 12 on main drive shaft 2 with rock-shaft lever 10 to convert the rotary motion of shaft 2 to reciprocating motion, which swings the rock shaft lever 10 back and forth to rock or oscillate the rock shaft 9.

As seen in diagrammatic FIG. 4, the eccentric 12 on shaft 2 has a center which is offset from the center of shaft 2 to provide an eccentricity equal to the radial difference between the circular locus 13 of its small radius and the circular locus 14 of its large radius. As a result, during each rotation of shaft 2, the pitman 11 reciprocates back and forth one time.

In accordance with the present invention, the location of the connection 15 of the pitman 11 to the rock shaft operating lever 10 may be progressively increased from the small radius R indicated in FIG. 3 to progressively larger radii to effect a progressive decrease in the length of the presser foot stroke. At the same time, the rock shaft 9, as it appears in FIG. 3, is turned angularly in the counter-clockwise direction to decrease the elevation of the bottom of the presser foot stroke.

In the presently preferred embodiment of the invention, the rock shaft lever 9 is provided with a slot 16 extending radially between rock shaft 9 and the outer end portion of its operating lever 10, a transverse opening 17 in its outer end portion, an adjusting screw 18 (extending from the pitman connection 15 radially through slot 16, opening 17 and the outer end portion of lever 10) with its inner end connected to connection 15 to pull or push that connection toward and hold it in a given position within the range of adjustment, and an adjusting nut 19 mounted on that portion of the screw 18 which extends through the outer end opening 17 of lever 10. Naturally, when nut 19 is turned one way, it will move screw 18 and connection 15 radially outward along slot 16 and, in so doing, force the lever 10 and rock shaft to turn in a direction corresponding to the counter-clockwise direction in FIG. 3. The radial outward movement of connection 15 progressively increased the radius of lever 10. This increase in radius effects a corresponding lessening in the length of the presser foot stroke together with a decrease in the elevation of the bottom of that stroke. In other words, it conditions the machine for sewing thinner materials by lessening and lowering the stroke.

In operation, we assume that the parts are positioned as seen in FIG. 3 wherein the machine is conditioned for sewing thick materials. In FIG. 3, the pitman 11 is at the end of its forward reciprocation and ready to begin its backward reciprocation. During the backward stroke of its reciprocation, the pitman swings it connection 15 (with the rock shaft lever 10) along a circularly arcuate path of the small radius. This arcuate path extends from the FIG. 3 position indicated in FIG. 4 at 21, through an angle approximating 50 in the FIG. 4 position indicated at 22.

In so doing, it turns the rock shaft 9 counter-clockwise (as seen in FIGS. 3-4) or in the direction indicated by the arrow used in FIGS. 2-4 to show the outer-most side of the rock shaft 9 as moving upwardly. As a result, the arm 8 moves the presser foot from the upper FIG. 5 elevation (shown at 21A) downwardly to the FIG. 5 elevation, shown at 22A. Naturally, during the forth portion of pitman lls reciprocation, it will return to its point 21 position and thereby raise the presser foot back to its 21A elevation.

If we now adjust connection 15 to increase the magnitude of radius R, that connection will move from point 21 of FIG. 4 outwardly to point 23. This adjustment lowers the top of the presser foot stroke from the high level indicated at 21A in FIG. 5 to the lower level 23A. Now, during the back portion of the reciprocation of pitman 11, it swings its connection 15 along an arcuate path extending along a circularly arcuate path of large radius. This arcuate path extends from the position indicated at 23 in FIG. 4 through an angle of 26 to the position indicated at 24. In doing so, it turns the rock shaft 9 counter-clockwise in FIGS. 3 and 4 and clockwise in FIG. 2 and thereby swings arm 8 downwardly to lower the bottom elevation of the presser foot 5 from the FIG. 5 elevation shown at 23A to the lower elevation shown at 24A in FIG. 5.

From the foregoing, it will be appreciated that I have provided a simply constructed easily operated means for easily and quickly adjusting the connection of the pitman 11 to the rock shaft lever to vary the radius of that lever from a short radius to a larger radius. The short radius provides, for each reciprocation of the pitman, a large rock shaft oscillation effecting a correspondingly large presser-foot reciprocation between a top limit and a bottom limit having an elevation high enough to accommodate a large sewing thickness. The larger radius provides, for each reciprocation of said pitman, a smaller rock shaft oscillation effecting a correspondingly smaller presser-foot reciprocation between a top limit and a bottom limit having an elevation low enough to accommodate a smaller sewing thickness.

Having described my invention, I claim:

1. In a sewing machine of the type having a rotary drive shaft for reciprocating a needle, an oscillating rock shaft for reciprocating a presser foot and motion conversion means interconnecting said shafts to convert rotary drive shaft motion into oscillating rock shaft motion, an improvement in said motion conversion means comprising:

(A) an eccentric for said drive shaft;

(B) a lever for said rock shaft;

(C) a pitman mounted on said eccentric for pitmanreciprocation purposes and connected to said lever for lever-oscillation purposes; and

(D) means for adjusting the connection of said pitman to the said lever to vary the radius of said lever 1) from a short radius providing, for each reciprocation of said pitman, a large rock shaft oscillation effecting a correspondingly large presser-foot reciprocation between a top limit and a bottom limit having an elevation high enough to accommodate a large sewing thickness,

(2) to a larger radius providing, for each reciprocation of said pitman, a smaller rock shaft oscillation effecting a correspondingly smaller presser-foot reciprocation between a top limit and a bottom limit having an elevation low enough to accommodate a smaller sewing thickness.

2. The improvement of claim 1 including:

(A) an adjustment screw mounted on the rock shaft lever and operative, when turned one way and the other, to move said pitman-lever connection radially back and forth for radius adjustment purposes.

References Cited UNITED STATES PATENTS 2,009,194 7/1935 Hleb 112-239 2,380,912 7/1945 Walter 112239 2,428,762 10/ 1947 Zeier 112235 2,445,297 7/1948 Zeier 112-2l2 PATRICK D. LAWSON, Primary Examiner U.S. C1. X.R. 112-212 

